How to restrict Windows XP DHCP clients to a specific subnet?

Simon Hobson dhcp1 at
Thu Feb 13 13:59:21 UTC 2014

Ole Holm Nielsen <Ole.H.Nielsen at> wrote:

> Cool!  I like this, but where is the documentation of this?  Googling it didn't seem to give any hits...

It isn't really documented, it's one of those tricks that uses a function (or a side effect of it) for a different purpose to what it was provided for.

Basically, you can set a variable to be used elsewhere, and I assume this is probably documented (not used it myself, so never looked). A side effect of setting a variable is that it's stored in the leases file - hence if you want to put some information in the leases file (eg for debugging what classes have been matched) then setting a variable (which you never actually reference) will do it.

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